Valve driving apparatus

ABSTRACT

Disclosed herein is a valve driving apparatus. The valve driving apparatus includes at least one swing arm having one side corresponding to an upper side of a valve opening and closing a combustion chamber of an internal combustion engine; and a cam unit periodically pivoting the swing arm. Here, the swing arm performs a swing motion on the other side thereof by external manipulation to periodically compress the valve. The valve driving apparatus is capable of adjusting lift amounts of valves opening and closing a combustion chamber of an internal combustion engine.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. §119 of Korean Patent Application No. 10-2008-0113562, filed Nov. 14, 2008, which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a valve driving apparatus and, more particularly, to a valve driving apparatus that is capable of continuously adjusting lift amounts of valves opening and closing a combustion chamber of an internal combustion engine with a double-cam unit to provide optimum fuel economy and output.

2. Description of the Related Art

In general, an internal combustion engine of vehicles includes a combustion chamber in which fuel is burned to generate power. The combustion chamber is provided with a valve train, which includes intake/exhaust valves controlling the flow of intake and exhaust gases and is associated with a crankshaft to open and close the combustion chamber.

In a typical valve train, the valve is open in a constant lift amount by a cam having a predetermined configuration, so that the amount of intake or exhaust gas is restricted to a constant amount. Thus, with a design contemplated for low speed driving conditions, time and degree of valve opening are insufficient in high-speed drive conditions, and with a design contemplated for the high speed drive conditions, a reverse phenomenon occurs in the low speed drive conditions.

More specifically, since a general internal combustion engine tuned for high speed driving is set to have a high valve lift value, it exhibits good performance under high-speed conditions, but is very disadvantageous in terms of idle stability and low-speed torque characteristics under low speed conditions. On the contrary, the engine tuned for low speed driving provides good idle stability and low-speed torque under low-speed conditions but exhibits limited performance under high-speed conditions. However, a variable valve lift technique varies the lift amount of the valve corresponding to the high-speed and low-speed conditions, thereby providing merits both under low-speed and high-speed conditions.

Accordingly, it has been attempted in recent years to develop a technique for increasing a charging efficiency in addition to a multi-valve technique to enhance fuel economy and output. As a result, various techniques have been developed, for example a variable induction system (VIS), a variable valve timing (VVT) technique, and a variable valve lift (VVL) technique. The variable induction system changes a length or cross-sectional area of an intake manifold in accordance with suction resistance of air that varies in accordance with an engine speed. In the variable valve timing technique and the variable valve lift technique, the time and degree of opening the valve are adjusted in accordance with an engine speed to control overlap timing, thereby controlling the cylinder charging amount and the remaining gas amount.

In a conventional variable valve lift-type valve driving apparatus, however, since the lift amount of the valve cannot be varied and time of opening or closing the intake or exhaust valve is fixed in a constant state, the amount of intake or exhaust air cannot be adjusted, so that optimum fuel economy and output cannot be obtained corresponding to an engine operation state. Therefore, there is a need to provide a valve driving apparatus that overcomes such problems.

BRIEF SUMMARY

The present invention is conceived to solve the above problems of the related art, and an aspect of the invention is to provide a valve driving apparatus that is capable of precisely adjusting lift amounts of valves periodically opening and closing a combustion chamber of an internal combustion engine with a double-cam unit associated therewith in order to achieve optimum fuel economy and output.

According to an aspect of the invention, a valve driving apparatus includes: at least one swing arm having one side corresponding to an upper side of a valve opening and closing a combustion chamber of an internal combustion engine; and a cam unit periodically pivoting the swing arm. Here, the swing arm performs a swing motion on the other side thereof by external manipulation to periodically compress the valve.

The cam unit may include: a pivot member acting as a reference axis of the cam unit; a web member formed on the pivot member; a high rotary shaft forcibly rotated by an external force; a high lift cam formed on the high rotary shaft and including a high eccentric rod eccentrically rotated during rotation of the high rotary shaft; and a sub-cam unit connected to the web member and simultaneously operating one or more swing arms through the high eccentric rod during rotation of the high lift cam.

The sub-cam unit may include: a low rotary shaft rotatably connected to the web member; a cam body formed on the low rotary shaft; a follow arm formed on the cam body to be rotated in a direction of the swing arm by periodic compression of the high eccentric rod; a low lift cam formed on the low rotary shaft and including a low eccentric rod to periodically compress one side of each of the swing arms at the same time during rotation of the follow arm; and an elastic member elastically supporting the cam body.

The cam body may include the same number of low lift cams at opposite sides of the follow arm. The follow arm may be provided with a rotatable follow roller at a portion thereof where the follower arm directly contacts the high lift cam. The low lift cam may include a contact surface formed to support a center of each of the swing arm. The swing arm may include a rotatable swing roller disposed at a portion thereof contacting the contact surface.

The follow arm and the low lift cam may be extended from the cam body in different directions from each other.

The web member may be rotatably connected to the link shaft, and the link shaft may be connected to an actuation unit.

The actuation unit may include: a connecting rod connected to the link shaft; a link pin linked to the connecting rod; a screw member linked to the link pin and linearly reciprocating in a perpendicular direction to an axis of the link shaft to reciprocate the link shaft on the arcuate track; and a power transmission member formed around a circumference of the screw member and reciprocating the screw member in a forward and rearward direction when the power transmission member is forcibly rotated by an external force.

The actuation unit may include: an actuator having a receiving groove that receives the link shaft therein; and a screw member screwed to the actuator and linearly reciprocating the actuator in a forward and rearward direction to guide reciprocation of the link shaft on an arcuate track when the screw member is forcibly rotated by an external force.

The elastic member may be supported at one side thereof by the link shaft and at the other side thereof by the cam body. The sub-cam unit may be received in a housing, and the sub-cam unit and the housing may include oil passages connected to each other between the sub-cam unit and the housing to receive a lubricant from outside through the oil passages.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the invention will become apparent from the following detailed description given in conjunction with the accompanying drawings, in which:

FIG. 1 is a side section view of a valve driving apparatus mounted in a housing in accordance with one embodiment of the present invention;

FIGS. 2 and 3 are perspective views of connection between components of the valve driving apparatus in accordance with the embodiment of the present invention;

FIG. 4 is an exploded perspective view of the valve driving apparatus in accordance with the embodiment of the present invention;

FIGS. 5 to 8 are operational diagrams of the valve driving apparatus in accordance with the embodiment of the present invention;

FIG. 9 is a perspective view of a valve driving apparatus in accordance with another embodiment of the present invention; and

FIG. 10 shows oil passages formed in a valve driving apparatus in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION

Embodiments of the invention will now be described in detail with reference to the accompanying drawings. It should be noted that the drawings are not to precise scale and may be exaggerated in thickness of lines or sizes of components for descriptive convenience and clarity only. Furthermore, the terms as used herein are defined by taking functions of the invention into account and can be changed according to the custom or intention of users or operators. Therefore, definition of the terms should be made according to the overall disclosures set forth herein.

Referring to FIGS. 1 to 4, a valve driving apparatus according to one embodiment of the invention includes swing arms 100 and a cam unit 300, which can variably control lift amounts of valves 20 opening and closing a combustion chamber 10 in an internal combustion engine.

Each of the swing arms 100 has one side corresponding to an upper side of the valve 20, which opens and closes the combustion chamber 10, and performs a swing motion on the other side thereof by external manipulation to directly compress the valve 20 in a periodic manner. The swing arm 100 generates a constant profile of oscillation to allow the valve 20 to reciprocate in an up-down direction in a constant period. Accordingly, as the swing arm 100 rotates about the other side thereof to allow the one side thereof to periodically compress an upper side of the valve 20, the valve 20 can be open or closed, that is, reciprocate in the up-down direction.

Here, the swing arm 100 is provided at the one side thereof with the valve 20 to face a lower surface of the one side in the longitudinal direction of the swing arm 100, and at the other side thereof with a stationary support member 200 to face a lower surface of the other side thereof. Thus, the other side of the swing arm 100 is supported by a support member 200 such that the swing arm 100 can rotate about the other side thereof.

As such, the lower surface of the one side of the swing arm 100 comes into contact with the valve 20 and the lower surface of the other side of the swing arm 100 is in contact with the support member 200, so that the support member 200 continues to exert an upward force to the lower surface of the other side of the swing arm 100. Accordingly, the swing arm 100 is capable of rotating about the other side center P1 supported by the support member 200. In other words, an imaginary center line L1 connecting the other side center P1 with one side center P2 of the swing arm 100 is reciprocatively pivoted about the other side center P1 in a predetermined range of pivot angles.

Here, the support member 200 is securely mounted on a housing 30. A common structure may be used to mount the support member 200 on the housing 30. In addition, since the swing arm 100 is supportively connected to the support member 200 and the valve 20, the swing arm 100 is not easily vibrated or displaced. Here, the housing 30 is formed at an upper side of the combustion chamber 10. Various modifications may be made to the swing arm 100 and the support member 200.

As described above, the swing arm 100 is rotated about the other side thereof by an external force. Here, the cam unit 300 serves to periodically pivot the swing arm 100. The cam unit 300 includes a pivot member 310, web members 320, a high rotary shaft 330, a high lift cam 340, and a sub-cam unit 350.

The pivot member 310 acts as a reference axis of the cam unit 300. Thus, the pivot member 310 is secured inside the housing 30. Here, a single pivot member 310 may be provided to one inner side of the housing 30, but two pivot members 310 may be provided to opposite inner sides of the housing 30 to firmly support the web members 320, respectively. In this case, each of the web members 320 is rotatably connected to the corresponding pivot member 310. In other words, each of the pivot members 310 is rotatably fitted into the corresponding web member 320, which is rotated about the pivot member 310. It should be understood that, with the pivot members 310 rotatably inserted into the housing 30, the web members 320 may be integrally formed with the pivot members 310. In this embodiment, the pivot member 310 is shown as having a shaft shape, but various modifications may be made to the pivot member 310.

As such, the web member 320 is connected to the corresponding pivot member 310. In other words, the pivot member 310 is rotatably inserted into a lower side of the web member 320. Thus, the web member 320 can be rotated about the pivot member 310. It should be understood that with the web members 320 integrally formed with the corresponding pivot members 310 to rotate together, the pivot members 310 may be rotatably mounted on the housing 30. In this embodiment, the web member 320 is shown as having a plate shape, but various modifications may be made to the web member 320.

The high rotary shaft 330 is forcibly rotated by an external force. Particularly, the high rotary shaft 330 is supported by the housing 30. That is, opposite ends of the high rotary shaft 330 are rotatably supported on the opposite sides of the housing 30, respectively. With this configuration, the high rotary shaft 330 can be firmly supported.

The high rotary shaft 330 is provided with the high lift cam 340. The high lift cam 340 has a high eccentric rod 342 extending from one side thereof. With this configuration, the high lift cam 340 eccentrically rotates. In other words, at any time when the high lift cam 340 is rotated about its rotational axis P3 to position the high eccentric rod 342 extending from one side thereof at a predetermined location on the circumference thereof, the high eccentric rod 342 compresses the swing arms 100 and follow arms 353 of the cam unit 300 described below, so that the valves 20 opens and closes the combustion chamber 10 while reciprocating in the up-down direction.

Here, the high lift cam 340 rotates in the same direction and at the same speed as those of the high rotary shaft 330. The high lift cam 340 may be separably coupled to the high rotary shaft 330 or may be integrally formed therewith by molding. The separable coupling of the high lift cam 340 to the high rotary shaft 330 may be achieved by bolts and the like, particularly, by diffusion bonding.

On the other hand, the sub-cam unit 350 is connected to the web members 320. The sub-cam unit 350 serves to simultaneously operate one or more swing arms 100 in cooperation with the high eccentric rod 342 during rotation of the high lift cam 340.

The sub-cam unit 350 includes a low rotary shaft 351, a cam body 352, the follow arms 353, low lift cams 355, and elastic members 358.

The low rotary shaft 351 is secured to the web members 320 by press-fitting or the like. Here, although the low rotary shaft 351 may be rotatably linked to the web members 320, this configuration requires change of an oil passage 410 for supply of an oil to the cam body 352 and can cause rigidity deterioration of the housing 30.

Here, since a pair of web members 320 is provided to the cam unit 300 in this embodiment, the opposite ends of the low rotary shaft 351 support the corresponding web members 320, respectively. The low rotary shaft 351 is located below the high rotary shaft 330 inside the housing 30.

The cam body 352 is formed around the circumference of the low rotary shaft 351. The cam body 352 serves to support the follow arms 353 and the low lift cams 355. Here, the cam body 352 may be integrally formed with the low rotary shaft 351 or may be separably coupled thereto. Particularly, the cam body 352 may be formed in a ring shape to be inserted and rotatably coupled to the low rotary shaft 351. With this configuration, when the cam body 352 is rotated, the low rotary shaft 351 is rotated in the same direction and at the same speed as the cam body 352. The cam body 352 may have a variety of shapes. It should be noted that all of the follow arms 353 and the low lift cams 355 may be integrally formed with the low rotary shaft 351 using a mold.

Each of the follow arms 353 formed on the cam body 352 is reciprocatively pivoted in the direction of the swing arm 100 by periodic compression of the high eccentric rod 342. Here, a rotatable follow roller 354 may be provided to the follow arms 353 to minimize friction on contact points between the follow arms 353 and the high eccentric rod 342. Here, the sub-cam unit 350 may include a pair of follow arms 353 facing each other such that the follow roller 354 is rotatably interposed between the follow arms 353. It should be noted that the follow roller 354 may be rotatably mounted inside the follow arms 353 to protrude from upper and lower sides of the follow arms 353. Additionally, a central axis P6 of the follow roller 354 rotates along a circular track around a central axis P4 of the low rotary shaft 351.

The low lift cams 355 formed on the cam body 352 serve to periodically compress the corresponding sides of the swing arms 100 at the same time during rotation of the follow arms 353. At this time, each of the low lift cams 355 has a low eccentric rod 356 extending from one side thereof. With this configuration, the low lift cams 355 can be eccentrically rotated.

In other words, at any time when each of the low lift cams 355 is rotated about its rotational axis P4 to position the low eccentric rod 356 extending from one side thereof at a predetermined location on the circumference thereof, the low eccentric rod 356 repetitiously compresses the corresponding swing arm 100, so that the valve 20 opens and closes the combustion chamber 10 while reciprocating in the up-down direction.

The follow arms 353 and the low lift cams 355 may be integrally formed with the cam body 352 and extend from the cam body 352 in different directions from each other. Particularly, the low eccentric rod 356 of the low lift cam 355 may be located lower than the follow roller 354 of the follow arm 353 on the cam body 352. This configuration serves to allow the low eccentric rod 356 to compress the one side of the corresponding swing arm 100 while being minimally pivoted when the follow roller 354 is rotated by compression of the high eccentric rod 342.

The cam body 352 may have the same number of low lift cams 355 at opposite sides of the follower arms 353. In other words, a plurality of low lift cams 355 is formed on the cam body 352 to compress the corresponding swing arms 100. At this time, the same number of low lift cams 355 may be formed at the opposite sides of the follower arms 353 to provide at least one pair of low lift cams 355. If the cam body 352 has a different number of low lift cams 355 at the opposite sides of the follower arms 353, slightly different rotational moments can be generated to cause unbalanced behavior of the swing arms 100. For descriptive convenience, the cam body 352 is shown as having a single low lift cam 355 at either side of the follower arms 353 to have a pair of low lift cams 355.

On the other hand, the cam body 352 is resiliently supported by the elastic members 358. This serves to maintain the follow roller 354 and the high lift cam 340 in close contact with each other during operation and to prevent the inertial force of the cam body 352 from being transferred to the swing arms 100.

If the high lift cam 340 is separated from the follow roller 354 during operation, various problems such as noise and valve jumping can occur. Noise generation can cause fatigue failure resulting from repetitious impact and the higher the speed with which such a phenomenon occurs, the greater the inertial force of the cam body 352. As a result, as soon as the high lift cam 340 of the high rotary shaft 330 pushes the follow roller 354 of the low lift shaft 351, a degree of opening the valve 20 is increased over a desired degree by the inertial force of the cam body 352. Accordingly, it is desirable that the elastic members 358 firmly support the cam body 352.

More specifically, each of the elastic members 358 is coupled to the low rotary shaft 351 to be supported at one side thereof by a link shaft 360 described below and at the other side thereof by the cam body 352. It should be understood that the opposite sides of the elastic member 358 may be supported at different positions. In this embodiment, the elastic member 358 may be a torsion spring. It should be understood that the invention is not limited thereto and a variety of mechanical elements may be used as the elastic member 358 as long as they can perform the function of the elastic member in this embodiment. Further, a pair of elastic members 358 may be provided to opposite sides of the low rotary shaft 351 to resiliently support the opposite sides of the cam body 352 with the same force.

With this configuration, each of the elastic members 358 is supported at one side thereof by the link shaft 360 to elastically support the cam body 352.

The low lift cam 355 may be formed with a contact surface 357 to support the center of the swing arm 100. The contact surface 357 serves to compress an upper side of the swing arm 100 in order to maintain the swing arm 100 in a state of being supported by the bottom surface of the housing 30. When the low eccentric rod 356 of the low lift cam 355 compresses the one side of the swing arm 100, the contact surface 357 may be brought into slight contact with the center of the swing arm 100 or may be slightly separated from the swing arm 100. This is for the purpose of minimizing friction between the contact surface 357 and the swing arm 100. Here, a swing roller 110 is rotatably mounted on an inner center of the swing arm 100 and exposed upward to directly contact the contact surface 357. The swing roller 110 has a central axis P5 at the center of the center line L1 connecting the other side center P1 with the one side center P2 of the swing arm 100.

On the other hand, the link shaft 360 rotatably connected to the web members 320 is connected to an actuation unit 370. The actuation unit 370 serves to adjust the compression of the low lift cam 355 on the one side of each of the swing arms 100 depending on a slanted degree of the follower arm 353 which varies by movement of the link shaft 360 along an arcuate track about the pivot member 310.

For example, the actuation unit 370 includes a connecting rod 371, a link pin 372, a screw member 373, and a power transmission member 374.

The connecting rod 371 is connected to the link shaft 360 to directly push the link shaft 360 upon application of an external pushing force of linear reciprocation. Since the link shaft 360 is connected to the connecting rod 371, it moves along with the connecting rod 371 and is provided to the web members 320, which are rotatably mounted on the pivot member 310. As a result, the web members 320 are capable of reciprocating along an arcuate track together with the link shaft 360 about the pivot member 310. The connecting rod 371 may be integrally formed with the link shaft 360 or may be separably mounted on the link shaft 360. Further, various modifications may be made to the connecting rod 371.

Additionally, the link pin 372 is linked to the connecting rod 371, and the screw member 373 is linked to the link pin 372 and linearly reciprocates perpendicular to an axis of the link shaft 360 to induce reciprocation of the link shaft 360 on the arcuate track. The power transmission member 374 is formed on the circumference of the screw member 373 and reciprocates the screw member 373 in a forward and rearward direction while being forcibly rotated by an external force.

Namely, when the power transmission member 374 is rotated by the external force, the screw member 373 is linearly moved forward and rearward by a rotational force of the power transmission member 374 and the connecting rod 371 is reciprocated by the external force in the forward and rearward direction from the link pin 372 to thereby control the link shaft 360 to reciprocate along the arcuate track.

The screw member 373 may include, but is not limited to, a ball screw as well as a variety of mechanical elements. Further, the power transmission member 374 may be a nut which is capable of being rotated by an external force. The power transmission member 374 is connected to a power generator 374 a such as a motor and the like. The power generator 374 a may be fastened to the power transmission member 374 by a bolt. The power generator 374 a serves to restrict the power transmission member 374 so as not to move in the axial direction of the actuation unit 370 during movement or stoppage of the power transmission member 374.

FIGS. 5 to 8 are operational diagrams of the valve driving apparatus in accordance with the embodiment of the invention.

Referring to FIG. 5, the actuation unit 370 is operated such that the imaginary line L2 connecting the central axis P5 of the swing roller 110 to the central axis P4 of the low rotary shaft 351 is perpendicular to the center line L1 connecting the other side center P1 of the swing arm 100 to the one side center P2 thereof, in a state wherein the swing arm 100 is not compressed by the low lift cam 355, so that the swing arm 100 is not pivoted and the valve 20 closes the combustion chamber 10.

The contact surface 357 of the low lift cam 355 is in slight contact with the swing roller 110 to thereby support the upper side of the swing arm 100 in the downward direction.

In addition, the high lift cam 340 contacts the follow roller 354 between the follow arms 353, with the high eccentric rod 342 of the high lift cam 340 directed opposite the follow roller 354.

Descriptions of other components are the same as those described in the above embodiment and will be omitted herein.

FIG. 6 shows that the high rotary shaft 330 is rotated by an external force in a state wherein the power transmission member 374 is stopped and the imaginary line L2 is perpendicular to the center line L1 connecting the other side center P1 of the swing arm 100 to the one side center P2 thereof.

When the high rotary shaft 330 is rotated by the external force, the high lift cam 340 is rotated together with the high rotary shaft 330, so that the high eccentric rod 342 compresses the follow roller 354 of the follow arm 353 for a predetermined duration.

When the high eccentric rod 342 compresses the follow roller 354, the low lift cam 355 is rotated in the same direction as the cam body 352 as soon as the cam body 352 is rotated. Then, the low eccentric rod 356 compresses one side of the corresponding swing arm 100. Accordingly, the valve 20 opens (or closes) the combustion chamber 10.

Particularly, when the follow roller 354 is compressed by a portion of the high eccentric rod 342 corresponding to an end of the longest axis (r) from the central axis P3 of the high rotary shaft 330, the valve 20 is completely lowered to a predetermined distance D1, thereby maximally opening the combustion chamber 10 within a preset range. Here, as the high eccentric rod 342 continues to compress the follow roller 354 in a predetermined round section, the valve 20 opens (or closes) the combustion chamber 10 by a pushing force of the swing arm 100.

Descriptions of other components are the same as those described in the above embodiment and will be omitted herein.

In FIG. 7, the power transmission member 374 is rotated to allow the connecting rod 371 and the web member 320 to rotate along an arcuate track about the pivot member 310.

In other words, FIG. 7 shows that the imaginary line L2 is slanted to the center line L1 in a state wherein the swing arm 100 is not compressed by the low lift cam 355 so that the swing arm 100 is not pivoted and the valve 20 closes the combustion chamber 10.

When the screw member 373 is linearly retracted, the web member 320 and the low rotary shaft 351 are moved a predetermined distance “A” along an arcuate track in the counterclockwise direction.

Here, the central axis P6 of the follow roller 354 is moved the same distance as the predetermined distance “A”, by which the web member 320 and the low rotary shaft 351 are moved along the arcuate track in the counterclockwise direction, so that the follow arm 353 is lifted a predetermined height in the counterclockwise direction about the central axis P4 of the low rotary shaft 351.

The contact surface 357 of the low lift cam 355 is in slight contact with the swing roller 110 to thereby support the upper side of the swing arm 100 in the downward direction. Thus, preferably, the swig roller 110 has a diameter so as to continue to contact the contact surface 357 moving along the arcuate track in an initial closed state of the valve 20.

In addition, the high lift cam 340 contacts the follow roller 354 of the follow arm 353, with the high eccentric rod 342 directed opposite the follow roller 354.

Descriptions of other components are the same as those described in the above embodiment and will be omitted herein.

FIG. 8 shows that the high rotary shaft 330 is rotated by an external force in a state wherein the power transmission member 374 is stopped and the imaginary line L2 is slanted to the center line L1.

When the high rotary shaft 330 is rotated by the external force, the high lift cam 340 is rotated together with the high rotary shaft 330, so that the high eccentric rod 342 compresses the follow roller 354 of the follow arm 354 for a predetermined duration.

When the high eccentric rod 342 compresses the follow roller 354, the low lift cam 355 is rotated in the same direction as the cam body 352 as soon as the cam body 352 is rotated. Then, the low eccentric rod 356 compresses one side of the corresponding swing arm 100. As a result, the valve 20 opens (or closes) the combustion chamber 10.

Then, when the follow roller 354 is compressed by a portion of the high eccentric rod 342 corresponding to the end of the longest axis (r) from the central axis P3 of the high rotary shaft 330, the valve 20 is completely lowered to a predetermined distance D2, thereby maximally opening the combustion chamber 10 within a preset range. Here, when the high eccentric rod 342 continues to compress the follow roller 354 in a predetermined round section, the valve 20 opens (or closes) the combustion chamber 10 by a pushing force of the swing arm 100.

The lowered distance D2 of the valve 20 with the center line L1 slanted to the imaginary line L2 is longer than the lowered distance D1 of the valve 20 with the center line L1 perpendicular to the imaginary line L2. This is attributed to the fact that, as the follow roller 354 is lifted a predetermined height with respect to the central axis P4 of the low rotary shaft 351 while being moved by the predetermined distance D1 along the arcuate track, the valve 20 is subjected to a greater pushing amount of the high eccentric rod 342 than in the other case.

Descriptions of other components are the same as those described in the above embodiment and will be omitted herein.

FIG. 9 is a perspective view of a valve driving apparatus including a drive unit in accordance with another embodiment of the present invention.

In this embodiment, a drive unit 370 of the valve driving apparatus includes an actuator 375 and a screw member 378.

The actuator 375 has a receiving groove 376 which receives a link shaft 360 therein. Here, since the link shaft 360 is moved along an arcuate track, the receiving groove 376 may have an elongated shape in the up-down direction or may have a hole shape which is open toward a lower side of the actuator 375.

Here, a plurality of actuators 375 may be formed on the link shaft 360 to actuate simultaneously, but only a single actuator 375 is shown as being connected to the link shaft 360 for convenience of description in this embodiment. Various modifications may be made to the actuator 375.

A screw member 378 is axially inserted into the actuator 375 in a perpendicular direction to an axial direction of the link shaft 360. Thus, when the screw member 378 is rotated by an external force, the actuator 375 is linearly reciprocated forward and rearward in the axial direction of the screw member 378. The screw member 378 may be a ball screw. The structure wherein the screw member 378 is rotated by an external force and the structure wherein the screw member 378 is rotatably positioned may be realized in various ways.

When the actuator 375 is linearly reciprocated in the forward and rearward direction, the link shaft 360 and web members 320 are reciprocated along an arcuate track about a pivot member 310.

The principle in variation of the lowered distance of the valves according to forward and rearward movement of the actuator 375 is the same as in the above embodiment.

Descriptions of other components are the same as those described in the above embodiment and will be omitted herein.

FIG. 10 shows oil passages 410 formed to minimize friction between respective components of the valve driving apparatus when a lubricant is supplied to the respective components through the housing 30.

The housing 30 is formed at one side thereof with an inlet 420 through which the housing 30 receives a lubricant. The housing 30 has an oil passage 410 defined from the inlet 420 to a portion thereof on which the support member 200 is mounted. The support member 200 can continue to support a lower surface of the other side of the swing arm 100 by a pushing force of the lubricant supplied through the oil passage 410.

The housing 30 is formed with another oil passage 410 from the inlet 420 to the pivot member. Then, the pivot member 310 guides the lubricant into the web members 320, which in turn guide the lubricant into the low rotary shaft 351. Then, the lubricant is supplied from the low rotary shaft 351 to the cam body 352 and is then discharged through an outlet 430 formed in the cam body 352 to flow towards contact portions between the high lift cam 340 and the follow rollers 354. Thus, the oil passage 410 is defined in the pivot member 310, the web members 320, the low rotary shaft 351, and the cam body 352.

It should be understood that the oil passage 410 may be formed along various paths so as to flow to various contact portions between all of the components.

As apparent from the above description, according to one embodiment of the invention, the valve driving apparatus is capable of precisely adjusting lift amounts of valves periodically opening and closing the combustion chamber through adjustment of a rolling contact area and a cam separation of a double-cam unit cooperatively connected thereto, thereby realizing optimum fuel economy and output. Further, according to another embodiment of the invention, a high rotary shaft having an upper side cam of the double-cam unit mounted thereon is not directly connected to a low rotary shaft having a lower side cam of the double-cam unit, thereby allowing the separation between the cams of the double-cam unit to be easily adjusted. Moreover, according to a further embodiment of the invention, a pair of web members connected to opposite ends of the low rotary shaft is simultaneously pivoted in the same direction and at the same speed to allow the low rotary shaft to move along an arcuate track while maintaining its axial direction, so that a plurality of valves can be controlled to have the same lift amount.

In understanding the scope of the invention, the use of articles “a,” “an” and “the” in the context of describing the invention, especially in the context of the embodiments, are to be construed to cover both the singular and the plural, unless otherwise indicated or clearly contradicted by context.

Although some embodiments have been provided to illustrate the invention in conjunction with the drawings, it will be apparent to those skilled in the art that the embodiments are given by way of illustration only, and that various modifications, changes, substitutions, and equivalent embodiments can be made without departing from the spirit and scope of the invention. The scope of the invention should be limited only by the accompanying claims. 

1. A valve driving apparatus, comprising: at least one swing arm having one side corresponding to an upper side of a valve opening and closing a combustion chamber of an internal combustion engine, the swing atm performing a swing motion on the other side thereof by external manipulation to periodically compress the valve; and a cam unit periodically pivoting the swing aim.
 2. The valve driving apparatus according to claim 1, wherein the cam unit comprises: a pivot member acting as a reference axis of the cam unit; a web member formed on the pivot member; a high rotary shaft forcibly rotated by an external force; a high lift cam formed on the high rotary shaft and including a high eccentric rod eccentrically rotated during rotation of the high rotary shaft; and a sub-cam unit connected to the web member and simultaneously operating the at least one swing arm through the high eccentric rod during rotation of the high lift cam.
 3. The valve driving apparatus according to claim 2, wherein the sub-cam unit comprises: a low rotary shaft rotatably connected to the web member; a cam body formed on the low rotary shaft; a follow arm formed on the cam body to be rotated in a direction of the swing arm by periodic compression of the high eccentric rod; a low lift cam formed on the low rotary shaft and including a low eccentric rod to periodically compress one side of the corresponding swing arm at the same time during rotation of the follow arm; and an elastic member elastically supporting the cam body.
 4. The valve driving apparatus according to claim 3, wherein the cam body comprises the same number of low lift cams at opposite sides of the follow arm.
 5. The valve driving apparatus according to claim 3, wherein the follow arm is provided with a rotatable follow roller at a portion thereof where the follower arm directly contacts the high lift cam.
 6. The valve driving apparatus according to claim 3, wherein the low lift cam comprises a contact surface formed to support a center of the swing arm.
 7. The valve driving apparatus according to claim 6, wherein the swing arm comprises a rotatable swing roller disposed at a portion thereof contacting the contact surface.
 8. The valve driving apparatus according to claim 3, wherein the follow arm and the low lift cam are extended from the cam body in different directions from each other.
 9. The valve driving apparatus according to any one of claims 2 to 8, wherein the web member is rotatably connected to the link shaft, and the link shaft is connected to an actuation unit, the actuation unit adjusting a compression amount of the low lift cam on the one side of the swing arm depending on a slanted degree of the follow arm that varies according to movement of the link shaft along an arcuate track about the pivot member.
 10. The valve driving apparatus according to claim 9, wherein the actuation unit comprises: a connecting rod connected to the link shaft; a link pin linked to the connecting rod; a screw member linked to the link pin and linearly reciprocating in a perpendicular direction to an axis of the link shaft to reciprocate the link shaft on the arcuate track; and a power transmission member formed around a circumference of the screw member and reciprocating the screw member in a forward and rearward direction when the power transmission member is forcibly rotated by an external force.
 11. The valve driving apparatus according to claim 9, wherein the actuation unit comprises: an actuator having a receiving groove that receives the link shaft therein; and a screw member screwed to the actuator and linearly reciprocating the actuator in a forward and rearward direction to guide reciprocation of the link shaft on an arcuate track when the screw member is forcibly rotated by an external force.
 12. The valve driving apparatus according to claim 9, wherein the elastic member is supported at one side thereof by the link shaft and at the other side thereof by the cam body.
 13. The valve driving apparatus according to claim 9, wherein the sub-cam unit is received in a housing, and wherein the sub-cam unit and the housing comprise oil passages connected to each other between the sub-cam unit and the housing to receive a lubricant from outside through the oil passages. 